Process of obtaining pure pyroligneous acid.



-dom of Prussia, German Empire, have in- Ooncentrating PyroligneousAcid, (for which one acid the elfort has been made to destroy UNITEDSTATES Patented August 25, 1903.

PATENT OFFICE,

GUSTAV GLOCK, OF BERLIN, GERMANY.

$PEG IFIGATION forming part of Letters Patent No. 736,959, dated August25, .1903.

Applioation filecl February 1 2, 1 902.

To all whom it may concern:

Be it known that I, GUSTAV GLooK, a subject of the Grand Duke of Baden,residing at No. 23 Gleditschstrasse, Berlin, in the Kingvented anImproved Process of Purifying and I have made application for LettersPatent in Germany, Serial No. G. 15,898, dated July 19, 1901; inAustria, dated November 27, 1901; in France, Serial No. 305,046, datedNovember 27, 1901; in Belgium, Serial No. 127,337, dated December 5,1901, and in Hungary, Serial No. 17,548,.dated December 12, 1901,) ofwhich the following is a specification.

My invention relates to an improved process of treating raw orpartly-purified pyroligneous acid with the view of simultaneouslypurifying and concentrating the same.

The raw pyroligneous acid obtained by the carbonization of woodcontains,besides water, tar, and wood-alcohol, from six to twelve percent. of acetic acid. The wood-alcohol may be easily separated from thepyroligneous acid by distillation; but distillation cannot be employedfor eliminating the tar from the pyroligneous acid, because tar andtar-like matter have the property of passing over with the vapors ofwater and acetic acid when subjected to distillation. It is equallyimpossible to eliminate water from the pyroligneous acid-v3. e., toconcentrate said acid by way of distillation. The only way hithertofound practicable to obtain pure acetic acid ofhigh concentration hasbeen to bind the aqueous pyroligneous acid to a base, to purify andconcentrate the acetate obtained, and, finally, to decompose the saidacetate by concentrated mineral acid. 1

For the purpose of purifying the pyrolignethe impurities thereincontained by chemical, particularly by oxidizing, agents; but as thevalue of the aqueous pyroligneous acid is but small and the amount ofimpurities added is considerable the expense hitherto incurred inprocesses of this kind exceeded the value of the product obtained. Forthis reason no process of purification based upon the use of chemicalmeans could be adopted in practice for operating on a large scale.

For the purpose of concentrating the pyro- Serial No. 93,787. (Nospecimens.)

ligneous acid various means tending to abstract water, such asconcentrated sulfuric acid or anhydrous neutral salts, have beenemployed, but without practical success. If sulfuric acid be employed,it is impossible to subsequently separate the same entirely from theacetic acid, and besides the sulfuric acid has a chemical action uponthe acetic acid and its impurities if temperature is raised to a certaindegree, and, further, the diluted and impure sulfuric acid obtained bysuch treatment could not be easily concentrated at small expense forrepeated use.

If anhydrous neutral salts be employed, it has been found that suchsalts not only crystallize with water of crystallization, but also withacetic acid, performing the same part in the crystals as water ofcrystallization does ordinarily, whereby the elimination of Water fromthe acetic acid is rendered impossible.

For these reasons none of the numerous processes proposed forconcentration could be employed in practice on a large scale.

By the process of my invention hereinafter described I am able toperform in one operation the purification from tar and the abstractionof water from the pyroligneous acid, thus simultaneously purifying andconcentrating the said acid.

This process is based upon the property of acid alkaline sulfates of notonly eliminating tar-like matters from pyroligneous acid, .but also ofbinding water in a higher degree than acetic acid.

It should be mentioned that Vincent has before made the observationonthe occasion of preparing chemically-pure acetic acid that bydecomposing pure crystallized acetate of soda by means of twoequivalents of sulfuric acid the bisulfate of soda obtained binds thewater of crystallization of the acetate of soda in such manner thatduring subsequent distillation strong acetic acid will pass over firstand afterward aqueous acid; but observations of such kind have not beenemployed by Vincent for effecting the concentration of free acetic acid.7

If bisulfate of soda is dissolved in raw pyroligneous acid previouslyfreed of wood-alcohol, the greater part of the tar contained in the saidacid will be separated, forming at 4 the surface a stratum of oilymatter, which a may be removed by filtration or by drawing off the-liquid'solution below said stratum. The solution thus obtained isclear, of a yellow color of wine, and becomes turbid on standing. Onsubjecting this fluid todistillation acetic acid will pass over, showingalready a high degree of purification. Though it still contains sometar, it will when bound to lime form an acetate of lime of eightysevenup to ninety per cent., while by employing any process hitherto in usethe acetate of lime obtained will only hold from eighty to eighty-twoper cent. On examining the several fractions of distillation of thepyroligneous acid it will be found that provided the bisnlfate was addedin certain proportions fnrther to be described the first fractions willdeliver the strongest acid, while the following fractions will becomeweak and the latest fractions will consist only of water.

I have found that the acid alkaline sulfate which answers bestds theprimary sulfate of soda, (NaHSO called 'bisulfate; but the tri and tetrasulfates of sodium or of potassium might equally be employed withsuccess. The primary sulfate of potassium (KHSO is, however, in some wayobjection able, for the reason that on reaching a certain degree oftemperature and of concentration it will suddenly become solid, therebysetting free so much heat that the whole amount of Water present will beconverted into steam,

I causing almost an explosive efiect. The proport-ions of the quantityof acetic acid and of the bisnlfate to be added may vary within widelimits. They are determined by the result to be obtainedt'. a, whetheronly purification of the acetic acid orits simultaneous concentration isto be efiected.

If, as an example, an aqueous pyroligneous acid of six per cent.is'being treated with onehalf to two-thirds of its weight of bisnlfate,the product of distillation will be nearly free of tar, but noconcentration will be obtained. This mode of proceeding will beadvisable if the raw pyroligneous acid contains a considerable'quantityof tar. If the acid to be treated contains but a small quantity of tar,an addition of a double or treble quantity of hisnlfate brought into theacid will not only lead to its purification, but also a high degree ofconcentration. A pyroligneous acid of high degreesof concentration willrequire comparatively inferior quantities of bisnlfate to be addedbefore distillation.

According to the quantity of bisnlfate employed distillation may becarried on under a vacuum during the whole or part of the operation.

In carrying into practice the process of my invention I prefer toproceed as follows: Owing to the considerable amount of tar contained inthe raw material at the beginning, the first distillation should becalculated rather to purify than to concentrate the pyroligneous acid.For this purpose between one and two parts of bisnlfate are added to-twoparts of pyroligneous acid. The solution is prepared in a suitablereceptacle by applying heat. When the tar has been separated, as alreadydescribed, the clear and, if desired, filtered solution is brought intoa still having neither column nor condenser, but being directlyconnected to the refrigerator. Distillation is now carried on, and itmay be effected under a vacuum during the whole operation or only duringpart of it. The products of distillation are collected by fractions.Distillation is stopped as soon as almost nothing more is passing overor when the contents of the still are strongly foaming.

Such foaming is caused by the tar, which being dissolved in the acidseparates from the solution of bisnlfate as the said solution becomesmore and more concentrated. After stopping the process of distillationthe contents of the still are brought back intothe receptacle where thesolution has been prepared, and while the said contents are still in aheated state a fresh quantity of raw pyroligneous acid to be treated isadded, such quantity being equal to that which has passed over bydistillation. The tar which has been separated from the solution duringthe first distillation, as described, will separate, together with thetar contained in said fresh quantity. Thus only one separation of tarwill be required for each quantity under treatment. When the liquid hasbeen withdrawn, it is again brought into the still and distillationcarried on as before. The same operation is constantly repeated. Thesame bisnlfate is employed over and over again for any number ofrepetitions.

The products of distillation obtained in the manner above described arefurther treated in the same manner. As has been stated before, theproducts of first distillation have been separated into fractions ofdifierent concentration. I collect those fractions of equalconcentration and submit the same to another distillation by addingbisnlfate, the quantity of which will vary between an equal portion upto the two-and-one-half-fold quantity, according to the state ofconcentration of the acid to be treated. If during such furtherdistillation only a small amount of tar is found remaining in the still,it will be sufficient to separate the tar from the bisulfateonly at theend of several successive operations, during which a greater amount oftar has been collecting. The presence of a trifling amount of tar is notobjectionable, as by being separated from the liquid it loses itsproperty of distilling over along with the vapors of water. The productsof second distillation are again collected by fractions of difierentconcentration. The fractions of equal concentration thereupon are againcollected and submitted to'further distillation by adding bisnlfate indue proportion to the state of concentration of the acid. In this mannerI proceed till the whole quantity of pyroligneous acid has been reducedto concentrated acid of sixty to seventy per cent. and residual waterholding but from nothing to two per cent. of acid. If the raw materialhad been an acid of ten per cent, such final result will be obtained bytwo distillations calculated upon the original quantity of thepyroligneous acid under treatment. An acid of ten per cent. will rendera degree'of concentration of from thirty-five to forty per cent. by thefirst fraction of distillation, and by submitting said first fraction toanother distillation the result will be aconcentration to from sixty toseventy per cent. The remaining water, holding but a small percentage ofacid, may preferably be treated in any known manner to form acetates, asit would not pay to push distillation further.

The-concentrated acid received by repeated distillation is completelyfree of tar and ready for use in the arts. It could not be used,however, for alimentary purposes on account of its containing homologousacids. Chemically-pure acetic acid and glacial acetic acid, however, maybe obtained from the product by any known process.

The novelty of my invention consists as well in the process'of purifyingthe pyroligneous acid by eliminating the tar through the agency of abisulfate and subsequent distillation, as also in the simultaneousconcentration of the .acid by means of fractioncd distillation of asolution of bisnlfate of pyroligneous acid.

The industrial merit of my invention consists in providing means forobtaining pure concentrated acetic acid without the necessity ofemploying the treatment by a salt of raw or partially-purifiedpyroligneous. acid, consisting in adding to the pyroligneous acid anacid sulfate of an alkali, and distilling the resultant solution.

2. The process of preparing acetic acid from raw or partially-purifiedpyroligneous acid, consisting in adding to the pyroligneous acid an acidsulfate of an alkali, and distilling by fractionated operations thesolution so prepared.

3. The process of preparing acetic acid from raw or partially-purifiedpyroligneous acid 4. The process of preparing acetic acid from raw orpartially-purified pyroligneous acid, which consists in dissolving anacid sulfate of an alkali in the pyroligneous acid, filtering, andsubsequently distilling said solution by fractionated operations.

5. The process of preparing acetic acid from raw or partially-purifiedpyroligneous acid, consisting in addingto the pyroligneous acidbisulfate of soda, and distilling the resultant solution.

6. The process of preparing acetic acid from raw or partially-purifiedpyroligneous acid, consisting in adding to the pyroligneous acidbisulfate of soda, and distilling by fractionated operations thesolution so prepared.

7. The process of preparing acetic acid from raw or partially-purifiedpyroligneous acid, which consists in dissolving bisulfate of soda in thepyroligneous acid, filtering, and subsequently distilling said solutionby fractionated operations.

In witness whereof I have hereunto set my hand in presence of twowitnesses.

GUSTAV GLOCK.

- Witnesses: v HENRY HASPER, WOLDEMAR HAUPT.

